This study is aimed at refining the phenotype for developmental phonology disorders by examining their comorbidity and phenotypic boundaries with language subtypes of phonology disorders and examine modes of inheritance for each subtype, while examining and allowing for gender differences that may exist. In addition, developmental phonology disorders will be compared to reading disorders, or dyslexia, in terms of phenotypic similarities and patterns of inheritance. The validity of family history in predicting later learning problems will also be examined, as will the value of testing battery measurements as predictors of the outcome of therapy for individuals with preschool phonology problems. Analytic activity has so far focused on covariate adjustment and admixture analyses of initial phonological measures. These analyses have established the existence of effects of gender and, to a lesser extent, of socio-economic status for these measures. Despite the use of age-specific norms, age effects were noted for most of the measures considered. To some extent, this may be attributable to the lack of available population figures for adult populations, but compensatory strategies in test-taking in adulthood represent another possibility. Approaches to adjust for this phenomenon, such as standardization within developmental epoch, are currently being considered.